Process for producing tert-leucine

Abstract

The present invention provides a method of producing tert-leucine, which includes reacting tert-leucine with substituted benzenesulfonic acid represented by the following formula (1) wherein R1 and R2 are each independently a hydrogen atom, an alkyl group or a halogen atom, except a compound wherein R1 and R2 are both hydrogen atoms, in a solvent, to give tert-leucine.substituted benzenesulfonate represented by the following formula (2) wherein R1 and R2 are the same substituents as above, separating the salt by crystallization and then dissociating the salt. According to the present invention, a production method of tert-leucine is provided, which includes forming a tert-leucine salt hardly soluble in a solvent and crystallization thereof to efficiently recover tert-leucine from the solvent.

1 . A method of producing tert-leucine, comprising: 
 reacting tert-leucine with a substituted benzenesulfonic acid represented by formula (1):                          wherein    R1 and R2 are each, independently, a hydrogen atom, an alkyl group or a halogen atom, with the proviso that R1 and R2 are not both hydrogen atoms,    in a solvent, to produce a tert-leucine-substituted benzenesulfonate salt represented by formula (2):                          wherein R1 and R2 are defined above;    separating the salt by crystallization; and then dissociating the salt.    
     
     
         2 . The method of  claim 1 , wherein the solvent is water.  
     
     
         3 . The method of  claim 2 , wherein the aqueous solvent has a pH of 0.1-3.0 during crystallization.  
     
     
         4 . The method of  claim 1 , wherein the tert-leucine is in an optically active form.  
     
     
         5 . The method of  claim 1 , wherein the alkyl group has 1 to 4 carbon atoms.  
     
     
         6 . The method of  claim 1 , wherein the alkyl group is a methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group or a tert-butyl group.  
     
     
         7 . The method of  claim 1 , wherein the alkyl group is a methyl group, ethyl group, n-propyl group or an isopropyl group.  
     
     
         8 . The method of  claim 1 , wherein the halogen atom is a fluorine atom, chlorine atom or bromine atom.  
     
     
         9 . The method of  claim 1 , wherein at least one of R1 and R2 is a hydrogen atom and the other is an alkyl group or a halogen atom.  
     
     
         10 . The method of  claim 1 , wherein at least one of R1 and R2 is a methyl group, ethyl group or chlorine atom.  
     
     
         11 . The method of  claim 1 , wherein the substituted benzenesulfonic acid represented by formula (1) is 3,4-dimethylbenzenesulfonic acid, p-toluenesulfonic acid, m-toluenesulfonic acid, p-ethylbenzenesulfonic acid or p-chlorobenzenesulfonic acid.  
     
     
         12 . The method of  claim 1 , wherein the substituted benzenesulfonic acid represented by formula (1) is 3,4-dimethylbenzenesulfonic acid.  
     
     
         13 . The method of  claim 1 , wherein the solvent is water and at least one of methanol and ethanol.  
     
     
         14 . A tert-leucine-substituted benzenesulfonate represented by formula (2):  
       
         
           
           
               
               
           
         
         wherein R1 and R2 are each, independently, a hydrogen atom, an alkyl group or a halogen atom, with the proviso that R1 and R2 are not both hydrogen atoms.  
       
     
     
         15 . The tert-leucine-substituted benzenesulfonate of  claim 14 , wherein the alkyl group has 1 to 4 carbon atoms.  
     
     
         16 . The tert-leucine-substituted benzenesulfonate of  claim 14 , wherein the alkyl group is a methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group or a tert-butyl group.  
     
     
         17 . The tert-leucine-substituted benzenesulfonate of  claim 14 , wherein the alkyl group is a methyl group, ethyl group, n-propyl group or an isopropyl group.  
     
     
         18 . The tert-leucine-substituted benzenesulfonate of  claim 14 , wherein the halogen atom is a fluorine atom, chlorine atom or bromine atom.  
     
     
         19 . The tert-leucine-substituted benzenesulfonate of  claim 14 , wherein at least one of R1 and R2 is a hydrogen atom and the other is an alkyl group or a halogen atom.  
     
     
         20 . The tert-leucine-substituted benzenesulfonate of  claim 14 , wherein at least one of R1 and R2 is a methyl group, ethyl group or chlorine atom.  
     
     
         21 . The tert-leucine-substituted benzenesulfonate of  claim 14 , wherein R1 and R2 are each a methyl group.  
     
     
         22 . The tert-leucine-substituted benzenesulfonate of  claim 14 , wherein R1 is a methyl group and and R2 is a hydrogen atom.  
     
     
         23 . The tert-leucine-substituted benzenesulfonate of  claim 14 , wherein R1 is a hydrogen atom and R2 is a methyl group.  
     
     
         24 . The tert-leucine-substituted benzenesulfonate of  claim 14 , wherein R1 is an ethyl group and R2 is a hydrogen atom.  
     
     
         25 . The tert-leucine-substituted benzenesulfonate of  claim 14 , wherein R1 is a chlorine atom and R2 is a hydrogen atom.